Inkjet printer and image formation method

Abstract

An object of the invention is to provide an inkjet printer that forms an image with good quality. The object is achieved by an inkjet printer 1 including an ink head H ejecting an ink, an ink supply unit P communicating with the ink head H, and an ink storage unit T communicating with the ink supply unit P and supplying the ink to the ink head H through the ink supply unit P, in which at least a part of the ink supply unit P has an ink heating unit S that heats the ink until a viscosity of the ink is within the range of 5 mPa·s or more to 30 mPa·s or less, and the ink storage unit T has a shearing device that shears the ink.

The invention claimed is: 
     
       1. An inkjet printer comprising:
 an ink head ejecting an ink; 
 an ink supply unit communicating with the ink head; and 
 an ink storage unit communicating with the ink supply unit and supplying the ink to the ink head through the ink supply unit, wherein 
 the ink supply unit has an ink heating unit that heats the ink until a viscosity of the ink is within the range of 5 mPa·s or more to 30 mPa·s or less, 
 the ink storage unit has a shearing device that shears the ink, 
 the ink storage unit includes a shearing device that has a rotation axis and a rotating blade provided at one end of the rotation axis and a container that accommodates the ink, and 
 the container is a substantially cylindrical container, and when a radius of a circle obtained by cutting the container in a horizontal direction with respect to a bottom surface is designated as R and a distance from the rotation axis to a leading end of the rotating blade is designated as r, r/R is equal to or more than 0.5. 
 
     
     
       2. The inkjet printer according to  claim 1 , being used for an ink having a viscosity at 25° C. of 5000 mPa·s or more. 
     
     
       3. The inkjet printer according to  claim 2 , wherein the shearing device decreases the viscosity of the ink to ⅕ or less of the viscosity of the ink before shearing. 
     
     
       4. The inkjet printer according to  claim 2 , wherein the ink contains a photopolymerizable compound, a photopolymerization initiator, and a gelling agent, and undergoes temperature-induced sol-gel phase transition. 
     
     
       5. The inkjet printer according to  claim 1 , wherein r/R is 0.60 to 0.77. 
     
     
       6. The inkjet printer according to  claim 1 , wherein, when the distance from the rotation axis to the leading end of the rotating blade is designated as r and a distance from the rotating blade to the bottom surface of the container is designated as d, r/d is 2 to 50. 
     
     
       7. The inkjet printer according to  claim 6 , wherein r/d is 4 to 30. 
     
     
       8. The inkjet printer according to  claim 1 , wherein a circumferential velocity of the rotating blade is 100 rpm to 600 rpm. 
     
     
       9. The inkjet printer according to  claim 1 , wherein the shearing device decreases the viscosity of the ink to ⅕ or less of the viscosity of the ink before shearing. 
     
     
       10. The inkjet printer according to  claim 1 , wherein the ink contains a photopolymerizable compound, a photopolymerization initiator, and a gelling agent, and undergoes temperature-induced sol-gel phase transition. 
     
     
       11. An image formation method comprising, in the following order:
 a step of shearing an active ray-curable inkjet ink in an ink storage unit; 
 a step of supplying the sheared active ray-curable inkjet ink to an ink head while the sheared active ray-curable inkjet ink is heated such that a viscosity of the ink is within the range of 5 mPa·s or more to 30 mPa·s or less; 
 a step of ejecting the active ray-curable inkjet ink to a recording medium; and 
 a step of curing the ink by irradiating the ink landed on the recording medium with an active ray, 
 wherein the ink storage unit includes a shearing device that has a rotation axis and a rotating blade provided at one end of the rotation axis and a container that accommodates the ink, and 
 the container is a substantially cylindrical container, and when a radius of a circle obtained by cutting the container in a horizontal direction with respect to a bottom surface is designated as R and a distance from the rotation axis to a leading end of the rotating blade is designated as r, r/R is equal to or more than 0.5. 
 
     
     
       12. The image formation method according to  claim 11 , wherein a viscosity at 25° C. of the active ray-curable inkjet ink is 5000 mPa·s. 
     
     
       13. The image formation method according to  claim 11 , wherein a circumferential velocity of the rotating blade is 100 rpm to 600 rpm. 
     
     
       14. The image formation method according to  claim 11 , wherein the shearing step decreases the viscosity of the ink to ⅕ or less of the viscosity of the ink before shearing.